Specific Requirement for the p85-p110α Phosphatidylinositol 3-Kinase during Epidermal Growth Factor-stimulated Actin Nucleation in Breast Cancer Cells*
- Karen Hill,
- Susan Welti‡,
- Jinghua Yu,
- James T. Murray,
- Shu-Chin Yip,
- John S. Condeelis‡,
- Jeffrey E. Segallठand
- Jonathan M. Backer§¶
- From the Departments of Molecular Pharmacology and of‡Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461
Abstract
We have studied the role of phosphatidylinositol 3-kinases (PI 3-kinases) in the regulation of the actin cytoskeleton in MTLn3 rat adenocarcinoma cells. Stimulation of MTLn3 cells withepidermal growth factor (EGF) induced a rapid increase in actin polymerization, with production of lamellipodia within 3 min. EGF-stimulated lamellipodia were blocked by 100 nm wortmannin, suggesting the involvement of a class Ia PI 3-kinase. MTLn3 cells contain equal amounts of p110α and p110β, and do not contain p110δ. Injection of specific inhibitory antibodies to p110α induced cell rounding and blocked EGF-stimulated lamellipod extension, whereas control or anti-p110β antibodies had no effect. In contrast, both antibodies inhibited EGF-stimulated DNA synthesis. An in situ assay for actin nucleation showed that EGF-stimulated formation of new barbed ends was blocked by injection of anti-p110α antibodies. In summary, the p110α isoform of PI 3-kinase is specifically required for EGF-stimulated actin nucleation during lamellipod extension in breast cancer cells.
Footnotes
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↵* This work was supported by a Scholar Award from the Irma T. Hirschl Trust and National Institutes of Health Grant GM55692 (to J. M. B.) and by a grant from the United States Army (to J. E. S.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵§ Established Scientist of the American Heart Associate (New York Affiliate).
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↵¶ To whom correspondence should be addressed: Dept. of Molecular Pharmacology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461. Tel.: 718-430-2153; Fax: 718-430-3749; E-mail: backer@aecom.yu.edu.
- Abbreviations:
- PI 3-kinase
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phosphatidylinositol 3-kinase
- EGF
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epidermal growth factor
- FITC
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fluorescein isothiocyanate
- GEF
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GTP exchange factor
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- Received November 15, 1999.
- Revision received December 8, 1999.
- The American Society for Biochemistry and Molecular Biology, Inc.
